315mhz antenna length

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New posts. Search forums. For a better experience, please enable JavaScript in your browser before proceeding. Thread starter ibrewster Start date Feb 12, I hope this is a good place to post this question. I am building a receiver to use with the CarLink mirror in my car so I can actually do something wit it other than just open the garage door.

I got everything hooked up and programed the way I wanted, and tested that it worked. Unfortunately, the range stank - I could be sitting in my car just outside the garage, and push the button, and the receiver just inside the garage would get nothing. Basically, it only seems to work reliably if there was absolutely nothing between the transmitter and receiver. After doing some research, I found a number of posts claiming that coil antennas can be tricky to get right, so with nothing to loose I tried straightening the wire and pulling it outside of the wooden box I installed everything in.

This did seem to help somewhat, and testing actually looked pretty good, but when I tried it from inside my car using the mirror buttons or the handheld remotesI was back to no real functionality - it would work if I had direct line of sight with no obstacles, but as soon as there was anything between transmitter and receiver, it was back to not receiving.

Further research informed me that the "ideal" antenna length would be So that leaves me with a few questions I'm hoping can be answered here: 1 The current coil antenna, once straightened, appears to be about the right length, but a significant portion of it is still inside the container, surrounded by other electrical stuff I have crammed in there.

Might putting a longer wire on, such that the Would that be likely to improve reception? I don't need the relays - all I need is to be able to generate a 4 channel digital output that I can feed into a micro controller Specifically, a CherryPy.

I'm not afraid of having to do a bit of programming, however. At the end of the day, I don't need a huge range.Forums New posts Search forums.

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315mhz antenna length

For a better experience, please enable JavaScript in your browser before proceeding. Thread starter chansen Start date Dec 11, Hi, I have built an electric sliding gate opener based on a 4Wd remote controil winch motor and curcuit. The mechanical have been working fine for 12 months now, but the electronics remain problematic. I bought a mhz 4 channel relay unit, which has a coiled wire antenna on the Rx unit.

I mounted the receiver atop the 6' high fence, in a weatherproof box, in order to get a good radio range. The units work fine as long as I stay within 20' of the receiver, with no metal between. Last edited: Dec 11, Boncuk New Member. Are you supplying the receiver and gate opener circuits off the same power supply? A metal fence or gate is no Faraday cage - hence radio waves will pass it.

Last edited: Dec 12, Hi boncuk, thanks for the reply.

315MHZ sucker antenna 315M wireless receiver module antenna SMA screw needle high gain 5dbi

The receiver is powered from the same 12V car battery as the winch motor. The relay then sends 12v down the wire 2 mtrs long the big 70Am,p relays toe make the motor go foreward or reverse as desired. If I put the tx close to the rx, it operates flawlessly. Hi chansen, to get rid of the relay chatter you might consider using separate power sources for the gate motor and the receiver. Increase antenna lenght to 43 or 86cm and try out if vertical or horizontal polarization increases range.

Boncuk said:. It is a Faraday cage for long wavelengths.Forums New posts Search forums. Media New media Search media. Classifieds New listings. Log in. Search titles only. Search Advanced search…. New posts. Search forums. For a better experience, please enable JavaScript in your browser before proceeding. Thread starter chrispitude Start date Dec 2, Status Not open for further replies. Hi folks! I have two Liftmaster LM garage door openers, which are jackshaft openers that get mounted on a front torsion spring: LiftMaster LM - Album on Imgur The range of the built-in "antenna" is terrible - there are MANY complaints about its range online.

If you look at the pictures, you'll see one long purple wire hanging straight ish down, and one short wire bent off to the side at a right angle ish. So I ordered two Liftmaster antenna extension kits. The kit contents are shown in the second picture.

It's an L bracket, an antenna, and a coax cable. However, the installation instructions say to cut off one end of the coax, unwind some outer braid, attach the braid to a ground source inside the opener, and solder the end of the inside coax conductor to the end of the long purple wire.

Quite frankly, this sounds like a dreadfully horrible way to install it. What I'd like to is to drill a hole and mount a male F jack somewhere on the opener. However, I'm not sure of the best electrical method for doing this. I'm a digital electronics E. Is that the proper way?

Which is appropriate, a balun or balun? Does the right answer depend on how the board-level impedance was designed? What's the purpose of the short purple wire? Is it possibly the same as ground? I can't tell without removing the board, which isn't trivial.

I included a picture of the antenna length. The openers operate at MHz. Is this a suboptimal antenna design? Another question - I have two openers and need two antenna extensions.

315mhz antenna length

Are there any restrictions on how the two remote antennas are mounted? Do I need to maintain any minimum separation distance, etc.? All advice is appreciated.

Whip Antenna Length And Frequency Calculator

Thanks everyone! Joined Jan 17, Messages 1.The example given was for a Bluetooth antenna with a frequency of MHz. The author then divided it by 4 to make a "quarter wave" antenna length of 30mm. Why divide it by 4 and what is the benefit of a "quarter wave" antenna. What is the effect of the conductor leading to the antenna? If the 30mm antenna is soldered to a 4mm lead, does that result in a 34mm antenna?

For a fractal antenna, should the 30mm length of wire be folded into a fractal shape or should the total fractal antenna be 30mm in width? I have read somewhere that one of the benefits of a fractal antenna is that they are able to receive signals of different wave lengths. Best Answer 10 years ago. A quarter wave antenna is sometimes used because it's shorter than a full wave antenna.

A quarter wave works better than a random wave antenna because of harmonics, I think that's the right word. THe feed line does not enter into the calculation if it is shielded wire or a balance line.

If you just feed the antenna with a hunk of wire then all of the wire not becomes an antenna and all of your design and math goes out the window, but less of your signal goes out of your antenna.

An antenna is able to receive a signal of any frequency. But frequencies that are multibles of dividibles of the antenna length are recieved much more stronger than those that are at odds with the math. Re-design is correct on everything except his feedline reasoning. SWR represents RF that is reflected and not collected or transmitted, therefore wasted radio waves. If your antenna is not resonant at the tuned frequency you lose much of the signal, possibly all of it.

You could create a simple dipole for your FM radio by taking a piece of two-conductor speaker wire, compute your size by taking the middle of the FM band, 98mhz would be close. Split the two wires apart at one end until each side is 1.

Tape it up at the junction where you reached 1. Spread the two separated sides at a 90 degree angle in a T shape. The 90 degree turn is what separates de-couples the radiator from the feedline. Spread your wires and use thumbtacs to keep it in place and you have a very effective FM antenna. Reply 6 weeks ago. Answer 7 years ago. Quick question. If you want to make a catch all antenna that would pick up everything from say short wave to UHF.

Could you use a short length antenna that is able to be divided from the wave length of many frequencies? Reply 9 months ago.

Common misconception raises dead post But, the higher the frequency denotes a shorter antenna. Pardoning my meticulously compulsive correction of spelling and grammar compare the above edited sentence with the author's originalI think I understand what you mean by "multibles of divisibles" -- after reading this knowledgeable answer multiple times -- and I also understand my having had so much trouble in math: Teachers who explained straightforward precepts with garbled grammar combined with "bassackwards" logorrhea diarrhea.

Think of a "sine wave" 12 cm long. Draw it on graph paper if you like. The first half goes positive, the second half goes negative. When catching an RF signal, "negative is just a phase change - you can divide the signal in half 6cm and say it starts and ends at zero. Dividing AGAIN for quarter wave 3cm : looking at your graph, the sine wave goes from zero to maximum. At the pointy end of your dipole, no current flows open circuit so, applying the sine wave, the other end with a connector has maximum signal current.But is is possible to create an antenna i.

Can it be done, will it work, and how would i be able to do it?

Antenna Magic part 1 - antenna, void, speed of light, frequency and wavelength

I've got two Separate modules - a transmitter and a receiver, not a transceiver. I need an antenna for both modules. Its not quite that easy. It depends on the application.

315mhz antenna length

For example, what radiation pattern do you wish to achieve and what bandwidth is the antenna expected to cope with. If you need a pattern that has high gain in front and behind the antenna but very little from the sides, then a quad loop antenna would be a good option, the width of this being the determining factor when designing for bandwidth. If you have two separate frequencies, ie one Tx and another one for Rx, then you can 'nest' the two quad loops together and the required antenna will only react to the applied frequency.

The added advantage of using a quad loop is that you are usually using the full wavelength and so the antenna is not losing its efficiency gain. If the radiation pattern required is different then a dipole or monopole could be the answer. As I said, it all depends on the application. The downside of using these designs is that you may have to reduce the length to a sensible proportion half wave or quarter wave and so lose a bit of gain.

The up-side is that the radiation spread will be much wider, although at a lower gain at the antenna. Please be aware though, that there is always a trade off between gain which can be loosely translated into sensitivity and bandwidth, it is extremely difficult, if not impossible to design a passive antenna with high gain and a large bandwidth unless you start getting into dish designs, LNA's etc.

Please also note that whatever design you opt for, the impedance must be maintained at 50 ohm otherwise other problems will creep in. You may have to use a Balun within the circuitry, it might be worth checking.

Antenna for dummies for 315MHz RF Receiver?

Thanks everyone! Update: I've got two Separate modules - a transmitter and a receiver, not a transceiver. Answer Save. Hi Its not quite that easy. Hope this helps. Note better check that nothing is using that frequency before transmitting because you can by fined if you cause an interference.

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Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up. My problem is that even though most blogs and Google searches for these modules use a quarter-wave length antenna roughly So my question is, how bad is it to use longer antennas?

Actually, it's not that strange. Like a VHF antenna on a car. Without this plane, the quarter wave antenna will not work properly. There is no harm in using a longer antenna. The reason for recommending a quarter wave antenna is probably that it has a higher antenna gain than the dipole, as well as the fact that it simply takes up less space It is also simpler than a "real" dipole.

The wikipedia articles on dipoles and monopoles are quite informative. Actually, many MHz circuit boards have a coil with a few windings between the circuitry and the solder pad marked ANT. When calculating the length of antenna elements, remember to use the propagation velocity that is less than "c," the velocity of EM radiation in free space.

Moreover, the velocity of EM radiation in a coaxial cable is much slower, and it is listed for each type of coaxial cable. This has dramatic importance if one is trying to tune a length of feeder cable The OP inquired about using a "longer wire" and I want to introduce caution to that point.

Johannes added, with excellence, that the OP really started out with a quarter-wave dipole that uses a phantom second half the earth, as a mirror to make a more proper antenna Proper orientation of the quarter-wave element I do not know how high above the earth this configuration must be; perhaps Johannes can answer that. More importantly, the half-wave dipole is FORGIVING to neophytes because of its simple "doughnut" omnidirectional radiation pattern, at right angles and all around, to the wire s.

In other words, it communicates with other antennas that share a mutual horizontal relationship. There is no gain in the direction of the wire itself A principal of "reciprocity" says that transmitting and receiving antennas share the same rule book! Well, that is easily taken, in low power situations like this. If you start using longer dipole antennas, you are instinctively searching for higher "gain.

You SHOULD adhere to the rule of using overall lengths that are odd multiples of half wavelength reduced by velocity factor. If your dipole is symmetric, that's good for novices.Here is a simple antenna calculator for two popular forms of ham radio HF wire antennas: the horizontal dipole and the inverted "V".

Enter your desired frequency MHz of operation i. If you have no particular preference within a given ham radio band, then simply enter its center frequency i. To fully understand the results obtained by this calculator, please take a few minutes to read the explanation below it. Be prepared to trim the ends of the inverted V dipole if the final frequency of resonance ends up being too low for your needs when the inverted V is installed in its permanent position.

The antenna calculator above uses this formula as a starting point to calculate wire lengths for the dipole. The results are conveniently displayed in inches, centimeters, feet and meters. This formula to obtain the length of a half-wave dipole antenna will give a good ballpark value to start with. However, the actual resulting frequency of resonance and feed-point impedance of a dipole will depend on:.

When each side of a dipole slopes down from the feed point, it is commonly called an inverted V. But if one were to actually do that, the inverted V would resonate at an even higher frequency! This will give you some leeway to trim the wire ends back if the inverted V resonates too low for your purpose when installed in its final position.

The formula used by the calculator to compute the wire lengths for the inverted V is based on the formula for a half-wave dipole. It is adjusted to take into account the special characteristics of the inverted V. In the case of the inverted V we must add - to the list of environmental variables influencing the half-wave dipole - the angle between the two legs of the inverted V.

The angle below the two sections of a horizontal dipole is degrees. As the two sections of the dipole are lowered below the feed point, the angle between the two legs decreases:. To avoid the latter outcome, the antenna calculator above is set up to compensate somewhat for local adverse environmental conditions. The length it will calculate will likely be a little too long. You will only have to trim it a few inches at a time to bring the frequency of resonance up to where you want it.

For more detailed information on ham radio HF wire antennas, please visit this section of our Web site. If the angle between the two legs of the inverted V becomes less than 90 degrees, the radiation patterns from each leg of the inverted V begin to interact and cancel each other to some extent.

Therefore, the angle between the two legs of an inverted V should not be less than 90 degrees. Remember, an inverted V requires slightly more wire than a horizontal dipole for a given frequency of resonance. The antenna calculator above will provide appropriate wire lengths for the inverted V and the dipole for a given frequency of your choice.

I am sharing this fitting video with you in these most challenging times. Let's keep the communication channels open while, by civic duty, we must maintain a vital physical distance from our fellow me…. Read More.

Installing a 315MHz Garage Door Antenna Extension

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